I have the X1900XT card in my Mac Pro 1,1, and the 30" ACD. Starting a day or two ago, the screen doesn't light up upon startup. The little white light is on the display indicating power, but the screen stays black. I wait for the machine to boot up to the login screen, and then I can unplug the DVI from the video card and plug it back, and the screen lights up. Which is dying, the card or the screen?